Endless, helical fibre, filtration centrifuge



Dec. 19, 1967 ENDLESS, Filed Sept. 21, 1966 J. PINKAVA 3,358,840

HELICAL FIBRE, FILTRATION CENTRIFUGE I 5. Sheets-Sheet l I: I: Ki 4517;: JILL FIG. 1

FIG. 2

INVENTOR. 76 7/ A a u'a ww ih 3,358,840 ENDLESS, HELICAL FIBRE,FILTRATIONICENTRIFUGEY Filed Sept. 21, 1966 J. PINKAVA Dec. 19, 1967 3Sheets-Sheet 2 mmm m" BEE-.

FIG. 3

" INVENTOR;

Dec. 19, 1967 J. PINKAVA 3,358,840

ENDLESS, HELICAL FIBRE, FILTRATION CENTRIFUGE Filed Sept. 21, 1966 5Sheets-Sheet 3 INVENTOR. Ja 11 2% K4 u-a United States Patent 3,358,840ENDLESS, HELICAL FIBRE, FILTRATION CENTRIFUGE Jan Pinlrava, Prague,Czechoslovakia, assignor to Ceskoslovenska akademie ved, Prague,Czechoslovakia Filed Sept. 21, 1966, Ser. No. 581,091 Claims priority,application Czechoslovakia, Sept. 30, 1965, 5,945/65 7 Claims. (Cl.210-370) ABSTRACT OF THE DISCLOSURE A filtration centrifuge comprisingopen-ended, ribbed inner and outer drums, the ribs of the inner drumbeing inside the ribs of the outer drum so that said inner drum isdriven by said outer drum, each drum having a hollow shaft, the shaft ofthe inner drum extending through the shaft of the outer drum, the axesof said drums being skewed so that a fibre introduced through the innerhollow shaft is wound in a helical path through the drums to form afilter surface inside said drums.

The invention relates to a continuous filtration centrifuge.

A continuous filtration centrifuge is known which consists of two ribbeddrums inserted one in the other so that their ribs engage into eachother. The axes of these drums are concurrent or skewed with respect toeach other. The ribs form the envelopes of these drums and their frontsare provided with holes arranged tangentially with respect to theinternal surface of the drum; through these holes passes a toroidallywound band of filtration cloth guided over the rounded edge of the outerdrum and a roller arranged on its front face, the front face of theinner drum 'being connected coaxially with a shaft passing through atleast one swingable bearing arranged in a hollow shaft of the outerdrum.

In consequence of the fact that the two axes of the ribbed drums areconcurrent or skewed with respect to each other the continuous band ofthe toroidally wound cloth is transported from the bottom of the drum toits second edge and it returns outside the drum through slots. Themother liquor and the wash waters are centrifuged by the toroidallywound band of filtration cloth whose turns overlap, and the filteredsuspension is thrown under effect of the centrifugal force from the edgeof the cloth into the respective trough. In consequence of theprogressive movement of the band which is arranged in the form of ahelix wound on the envelopes of the two drums there is created over theentire internal surface of the drum a coherent filtration surface;consequently, during rotation of the centrifuge the toroidally woundband can be washed and there is continuous centrifugation.

But this centrifuge with a toroidally wound band has no sufiicientfiltration capacity for fine suspensions and in some cases it is alsodifiicult to wash the band.

It is a general object of this invention to eliminate the abovementioned drawbacks.

The invention also relates to a continuous filtration centrifuge. Toachieve continuous filtration in this centrifuge there is used acontinuous fibre instead of the toroidally wound band. Compared with theknown centrifuge, the centrifuge in accordance with the invention usesalso a system of two ribbed drums whose axes are also either concurrentor skewed with respect to each other.

The main feature of the invention resides in the following facts; theinner drum is provided with a hollow shaft arranged by means of abearing in a hollow shaft of the outer drum; outside the centrifugethere is arranged ;a device for driving the continuous fibre which isprovided with a motor, and also a winding device which leads thecontinuous fibre from the inner space of the drums placed one into theother and over guide rollers. From this winding device the continuousfibre is returned to the device for driving the continuous fibre. Inconsequence of the centrifugal force during running of the centrifuge,the continuous fibre is wound in the form of a helix on the innersurface of the drum which produces a filtration layer for the suspensioninjected into the inner space of the two drums by a jet arranged nearthe tube for leading the fibre from the centrifuge.

The invention will be best understood from the following specificationto be read in conjunction with the accompanying figures in which:

FIGS. 1 and 2 explain how the fibre is moved on the two drums whose axesare concurrent or skewed with respect to each other;

FIG. 3 illustrates a section through the centrifuge;

FIG. 4 is a cross-section along the line I-II in FIG. 3; and

FIG. 5 illustrates another embodiment of the centrifuge. I

Referring now more particularly to FIG. 1, it is seen that the cylinders1 and 2 are mounted on axes 4 and 4' which are not parallel. A fibre 3is wound around the two cylinders. If one of the cylinders, for examplecylinder 1, rotates, cylinder 2 is also rotated by the effect of thefibre 3 acting as a sort of belt, and the fibre 3 moves in the directionof the axis 4 of the cylinder 2.

FIG. 2 explains the principle of the invention. g'Ihe two drums 1 and 2are inserted one into the other and engage one into the other by meansof bars or ribs 5 and 6. If now drum 1 is rotated, it rotates also drum2. The schematic illustration of FIG. 2 shows that the shaft 4 of drum 1is hollow and the shaft of the second drum 2 passes therethrough. Thebearings 7 of the shafts 4 and 4' can be adjusted slidaibly, and byadjusting one or the other of the bearings the shafts of the twocylinders can be made to extend concurrently. While the two drums 1 and2 rotate, the fibre moves in the direction of the axis of the drum. Thefibre 3 may also be placed on the inner surface of the bars or ribs ofdrum 2, and if the cylinders move so fast that the fibre 3 is pressed bycentrifugal force against the ribs 5, 6, the fibre moves in thedirection of the axes of the two cylinders, and the individual turns ofthe fibre progressively cover the entire inner surface of the ribs ofthe cylinders. This creates on the inner surface of the bars acontinuous layer of turns of the fibre placed side by side.

FIG. 3 illustrates schematically the arrangement of the entire device,that is a continuous filtration centrifuge, a dosing device and awinding device.

The centrifuge consists of two drums 1 and 2 whose cylindrical surfacesare not continuous or full but are made of individual ribs 5, 6 whichengage into each other, as shown in FIG. 4 which represents across-section of the two drums along the line I-II in FIG. 3. Therefore,if drum 1 with the ribs 5 rotates, it carries along the ribs 6 of thedrum 2 which is also rotated. The shaft 4 of the drum 1 is mounted inthe stationary bearing 7 which is connected with the casing of 29 of thecentrifuge. This shaft 4 is hollow, and the second shaft 4' of thesecond drum 2 passes therethrough. The second shaft 4' is also hollow toguide the fibre inside the drum 2, as will be explained below. Thesecond shaft 4' is mounted in the bearing 8 arranged in the first shaft4. The second shaft 4 can be shifted in this bearing through a smallangle. The shaft 4' is provided with a stationarily mounted ring 9against which rests on one side a micnornetric screw 10, and on theother side a spring 11. This device makes it possible to swing or shiftthe shaft 4' against the shaft 4 so that the axes of the two shafts arenot parallel, but for example concurrent. The shaft 4 of drum 1 isprovided on its end with a belt pulley 12 for driving this drum. Now, ifdrum 1 is rotated, drum 2 is also rotated due to the fact that the ribs5 of drum 1 engage with ribs 6 of drum 2, as shown in FIG. 4.

The fibre 13 which is guided into the drum 2 of the centrifuge is woundon the device for driving the continuous fibre. This device consists oftwo rollers 14 and 15 on which is placed the fibre which is guided inthe manner described below into the inner surface of drum 2 over rollers16 and via the winding device back to the roller 14 of the device fordriving the continuous fibre. The roller 14 is driven by the motor 17but this movement may also be derived from the drive of the two drums 1and 2. The fibre is therefore continuous and it is forcedly shifted. Thespeed of the movement of the fibre produced by the motor 17 can bechanged for example in several stages with respect to the speed of therotation of the drum. Changes of the speed are necesary if it isrequired to obtain a double or multiple layer of turns of the fibre onthe inner surface of the drum 2 of the centrifuge.

In order to facilitate introduction of turns of the fibre into thecentrifuge and to overcome the resistance produced by friction on thewalls of the hollow shaft 4, it is convenient to insert an ejectorbetween the device for driving the continuous fibre 14, 15, and thehollow shaft 4'. The ejector 18 directs the movement of the fibre 13 bya concurrent air or water stream so that no disturbances are producedbefore the fibre enters the hollow shaft 4. The air or Water is suppliedinto the ejector 18 by a tube 19 in the direction of the arrow shown inthe figure. This device permits a smooth creation of the filtrationlayer even at such rotations of the centrifuge where the centrifugalforce acting on the fibre is smaller than the resistance produced byfriction of the drawn loop. The fibre is guided from the ejector 18 bythe hollow shaft 4' to the bottom of the drum 2, and by action of thecentrifugal force it is placed on the inner surface of drum 2. Asillustrated schematically in FIGS. 1 and 2, due to the concurrent orskewed arrangement of the two axes or shafts 4 and 4', the individualturns of the fibre are placed close to each other and thus form a.filtration layer 20 comprising turns moving from the bottom of the drum2 to itsopen end. The fibre 13 is drawn from the raised edge 21 by thetube 22 laying in the axis of the shaft 4 at the open end of the drum 2via the guiding rollers 16 and the winding device to the device fordriving the continuous fibre 14, 15.

The winding device permits the continuous fibre to be wound off from thedrum at any time and to be again wound on into a filtration layer duringrunning of the centrifuge. This winding device consist of two pairs ofrollers 23, 24 arranged freely rotatable on the shaft 25. The rollers23, 24 are provided with circumferential grooves. The two shafts 25 arefastened to the frame 26 which is mounted on another shaft 27. Thecontinuous fibre is first wound on one pair of rollers and then in theopposite direction on the other one. Winding on or loosening is achievedby rotation of the entire device about the shaft 27 which is in commonto the two pairs of rollers. The fibre passes always from one groove ofthe upper roller into the next groove of the lower roller and finally itcrosses over to the second pair of rollers which rotates therefor in theopposite direction.

It should of course be understood that this device for locating theturns of the continuous fibre during running of the centrifuge may alsobe replaced by another device performing the same function.

The suspension to be filtered is injected into the drum 2 of thecentrifuge by a jet 28 located near the tube 22 through which the fibreis led out from the centrifuge. The centrifuged filtrate (for example acrystal mother liquor, a suspension medium, a dispersion) is captured ina respective part of the casing 29 of the centrifuge and it is led awaythrough the opening 3%, while the filtered rigid material thrown offfrom the edge of the drum is led away through a trough or a tube 31.

FIG. 5 illustrates another embodiment of the device by means of whichthe rotating continuous fibre is deviated from the path of the injectedsuspension. It consists of a tube 32 arranged coaxially with thecentrifuge drum in roller bearings which have not been shown in thedrawing. The tube 32 is provided on its end with a disk 33 made from ametal, plastic material, glass or another suitable material. The tube 32is set into rotation in such a manner that its rotations agree with therotations of the reed of the wound off fibre. The reed is deviatedwithout noticeable friction in the indicated manner so that thesuspension can now be sprayed on outside its path. The withdrawn fibreforms a rotating reed which would nor mally cross the stream of suppliedsuspension which has to be filtered. The suspension is inevitablyscattered and the withdrawn fibre is polluted. This is prevented by thedevice in accordance with FIG. 5.

The disk 33 is set into rotation corresponding to the rotation of thereed of the wound-0E fibre, and after creation of a filtration layer itis inserted as far as possible to the bottom of the centrifuge drum.Thus the rotating reed of the withdrawn fibre is deviated from the pathof the sprayed on suspension.

In the stationary state which is created by the function of thecentrifuge, a filtration layer is again and again created at the bottomof the drum by winding on the reed, and it is again wound off from theedge of the drum. It is obvious that the fibre returning to the drum canbe perfectly freed of remnants of the suspension stuck thereto so thatthe suspenion is filtrated all the time through a fresh and purefiltration layer. The fibre forms no gaps through which the suspensioncould flow. If by wrong manipulation a gap is formed, it is suflicientto increase the feed speed of the fibre to close the gap automatically.Before starting filtration, first the necessary filtration layer isformed, whereupon the centrifuge is maintained in the stationary stateWhere the supply speed (winding-on) of the fibre is the same as thespeed of withdrawal (windin oif), and continuous filtration is startedby supplying the suspension into the centrifuge.

A multiple layer of the loop is created by a corresponding increase inthe supply speed of the fibre which then becomes placed by itsindividual turns above each other in dependence on the ratio between thespeed of supply and withdrawal. For example, if the supply speed of thefibre is three times as high as the speed of withdrawal, there aredirectly formed triple turns and creation of the filtration layerproceeds otherwise in a normal manner, as when simple turns aredeposited.

While the centrifuge is running, the fibre circulates all the time at acertain speed which represents a certain fraction of the circumferentialvelocity of the centrifuge and, at the same time, the complete layer ofturns is moved from the bottom to the edge as a unit by the system oftwo rod or rib drums engaging into each other. It is obvious from theprinciple of the centrifuge into which the fibre is placed that thesupplied fibre is twisted and wound on the inner surface of the drum, orthere occurs twining which is proportional to the difference between therotations of the centrifuge or the circumferential velocity of thecarried fibre, and the speed of its movement through the entirecentrifuge. This is no drawback in the case of a continuous fibrebecause during withdrawal the fibre isalso cut up at the same ratio sothat the original twists, if any at all, remain the same outside thecentrifuge drum. Washing of the fibre can be arranged at any placebetween the discharge of the fibre from the drum and its new entry intothe drum. Washing is accomplished conveniently countercurrentwise, forexample so that the running fibre is led into a tube against a stream ofpure Water. If neces sary, the washing water can be returned into thecentrifuge to avoid even very small losses.

After washing or, if the fibre is not washed, after the fibre leaves thecentrifuge drum, the fibre may be led through another air ejector whereit is freed of excess liquid (water or another suspension medium) by aviolent stream of air, or of air and a liquid.

It should of course be understood that the various details of thedescribed device may be modified in different manners. For example, thedevice for driving the continuous fibre may comprise, instead of twogroove-d rollers, two or three rollers, of which at least one isprovided with a layer of rubber or a similar material, and the fibre ispressed between these rollers and forcedly guided. An other possibilityis using a tub-shaped body with a grooved roller. Instead of thedescribed device for Withdrawin g the fibre by means of which thewound-off reed of the fibre is deviated out of the path of the injectedsuspension, the same result may also be achieved, for example, bysynchronized interruption of the spraying-on action at the moment whenthe moment when the wound-ofl? fibre passes the mouth of the jet. Theinjector after the wind ingoif device may be replaced .by a pair ofwringing rollers. Other details and parts of the device may also bereplaced by other parts performing an equivalent function withoutexceeding the scope of the invention.

What I claim is:

1. Continuous filtration centrifuge, comprising:

an outer drum and an inner drum inserted in the said outer drum;

the envelopes of the said two drums each comprising a plurality of ribsand having their axes arranged with respect to each other in directionsdifferent from parallel, and the ribs of each of the two envelopesarranged with respect to each other so that if one of the two drums isrotated, the other is also rotated;

a hollow shaft on said outer drum;

a hollow shaft on said inner drum mounted in the said hollow shaft ofthe said outer drum;

a device with a motor for driving a continuous fibre;

a winding device which guides the continuous fibre from the inner spaceof the said two drums to the outside through a tube and over rollers;

means for guiding the continuous fibre back from the fibre windingdevice to the fibre driving device;

a jet near the said tube through which a suspension can be injected intothe inner space of the said two drums onto the filtration layer formedin consequence of the continuous fibre being wound by action of the 1,wherein the said fibre Winding device comprises:

a frame;

two shafts attached to the said frame; pins on which the said frame ismounted; and two grooved rollers freely rotatable on the said shaftsattached to the said frame. 5. Continuous filtration centrifuge asclaimed in claim 1, wherein the fibre leading away device comprises:

a tube locate-d shiftably in the axis of a centrifuge drum; the end ofthe said tube lying in the inner space of the said drum being providedwith a disk having a smaller diameter than the diameter of thefiltration layer formed by the said fibre; means for rotating the saidtube at a velocity Whose maximum value equals the velocity at which thesaid fibre is being wound off. 6. Continuous filtration centrifuge asclaimed in claim 4, wherein the fibre leading away device comprises:

a tube located shiftably in the axis of a centrifuge drum; the end ofthe said tube lying in the inner space of the said drum provided with adisk having a smaller diameter than the diameter of the filtration layerformed by the said fibres; means for rotating the said tube at avelocity whose maximum value equals the velocity at which the said fibreis being wound off. 7. Continuous filtration centrifuge as claimed inclaim 6, comprising:

an ejector between the fibre driving device and the hollow shaft of theinner drum; a tube connected with this ejector; means for producing aparallel stream of air and Water and supplying it through the tube andthe ejector for directing the movement of fibre.

No references cited.

REUBEN FRIEDMAN, Primary Examiner. F. SPEAR, Assistant Examiner.

1. CONTINUOUS FILTRATION CENTRIFUGE, COMPRISING; AN OUTER DRUM AND ANINNER DRUM INSERTED IN THE SAID OUTER DRUM; THE ENVELOPES OF THE SAIDTWO DRUMS EACH COMPRISING A PLURALITY OF RIBS AND HAVING THEIR AXESARRANGED WITH RESPECT TO EACH OTHER IN DIRECTIONS DIFFERENT FROMPARALLEL, AND THE RIBS OF EACH OF THE TWO ENVELOPES ARRANGED WITHRESPECT TO EACH OTHER SO THAT IF ONE OF THE TWO DRUMS IS ROTATED, THEOTHER IS ALSO ROTATED; A HOLLOW SHAFT ON SAID OUTER DRUM; A HOLLOW SHAFTON SAID INNER DRUM MOUNTED IN THE SAID HOLLOW SHAFT OF THE SAID OUTERDRUM; A DEVICE WITH A MOTOR FOR DRIVING A CONTINUOUS FIBRE; A WINDINGDEVICE WHICH GUIDES THE CONTINUOUS FIBRE FROM THE INNER SPACE OF THESAID TWO DRUMS TO THE OUTSIDE THROUGH A TUBE AND OVER ROLLERS;